Standard Bravo I is a widely known 4 blade propeller with remarkable performance. It is available in diameter 15 ¼" and in pitch sizes: 20", 21", 22", 24", 25", 26", 28", 30", 32", 34" και 36".
A few years ago Mercury introduced the «younger sister» of standard Bravo I propeller, the pro finished Bravo I FS which is available in a diameter of 15 ¼΄΄ and in pitch sizes from 20΄΄ to 33΄΄ in one inch increments.
As shown by its name, the pro finished Bravo I FS (Four Stroke) propeller is designed specifically for high-horsepower four-stroke outboard engines and is positioned somewhere between the standard and the lab finished Bravo I.
In other words, Bravo I FS is a new version of the standard Bravo I propeller in which some specific modifications of its characteristics have been made. The most important of these are the following:
- its exhaust barrel has been shortened
- the cup height of its blades has been reduced
- the leading edges of its blades has been become thinner and sharper
Therefore, Bravo I FS has been born from the above modifications which can increase the performance of our boat when it suits with the hull-engine combination.
These small, but so significant changes make Bravo I FS «lighter» for our engine, leading to an increase of its rpm comparing with a same pitch standard Bravo I propeller.
This by itself is very important because Bravo I FS gives us the opportunity to move up one or two inches of pitch keeping the same rpm as the shorter pitch standard Bravo I which leads to the increase of both the cruising speed and top speed.
Moreover, compared with the standard Bravo I, the FS can hold the bow higher and work wonderful when:
- our bow is standing very low during the ride
- we do not need so great stern lift by our propeller as for example in stepped hulls
- we don’t overload our stern.
Bravo I FS came to make waves on the usual way of choosing the right propeller.
- When we switch from a standard Bravo I propeller to a Bravo I FS we can increase the pitch by one inch and not only will not the engine’s rpm drop, but on the contrary, we will gain about 100 rpm more.
- In other words, when we switch from a standard Bravo I to a Bravo I FS of the same pitch, we should expect an increase of our engine rpm at about 250-300 rpm. This means that we have the opportunity to move up, for example, from a 22΄΄ Bravo I to a 24΄΄ Bravo I FS retaining at approximately the same rpm and so gaining higher top speed, higher mid-range cruise speed and less fuel consumption.
- If we are running a Revolution propeller we would go to a Bravo I FS increasing by two inches the pitch while not significantly reducing the engine’s rpm, improving thus the speed and fuel economy. In this case we might have a decrease of about 50 to 100 rpm.
- Even if we are running a 3-blade propeller such as the Tempest Plus or Mirage Plus we would switch to a longer one by one inch pitch Bravo I FS, maintaining the same engine’s rpm at WOT.
Never before could we switch from a 3-blade propeller with smaller diameter and shorter pitch to a 4-blade one with larger diameter and longer pitch without reducing the engine’s rpm.
This is precisely the great success of Bravo I FS.
Still, we will achieve all the above mentioned only with the ultimate condition: the design of our hull and weight distribution to «like» the Bravo I FS.